1. Field of the Invention
This invention relates generally to All Terrain and Mountain Bicycles and to a means for softening the ride over rough ground without sacrificing pedalling efficiency.
2. Description of the prior art
The only shock absorbtion feature of the most widely used Mountain Bicycles is that provided by oversize tires and the flexibility of the front forks. When riding in competition over rough ground on these mountain bicycles, the shock and vibration from gripping the handlebars can cause severe fatigue and cramping of the riders hands and forearms. One model in limited production (The Slingshot) adds flexibility to the frame to reduce the shock and vibration by replacing the down tube with a steel cable which terminates in a compression spring under the bottom bracket, and adding a kevlar spring at the joint between the top tube and the seat tube to allow the frame to flex without breaking. Another model uses a Hannebrink rear suspension with pivoted chain stays and a shock strut for the transfer of load on the rear wheel to the frame which allows the rear wheel to bounce with minimum disturbance to the frame. The cable/spring arrangement provides a slight softening of the ride coupled with a modest reduction in pedalling efficiency, while the Hannebrink arrangement provides considerable shock absorbtion with an equally considerable reduction in both pedalling efficiency and traction. Adding flexibility anywhere along the load path between the handlebars, bottom bracket and rear wheel detracts from pedalling efficiency because the loads imposed through pedalling flex the structure which absorbs energy and reduces the proportion of pedal power delivered to the rear wheel. Therefore, the only way to soften the ride without sacrificing pedalling efficiency is to add shock absorbtion to the front fork while maintening the frame, handlebars to rear wheel, as stiff as possible without adding weight.